Oxygen scavenging packaging

ABSTRACT

Oxygen scavenging materials incorporated into or attached to a package such as a gable-top or rectangular carton, used to package foods, beverages or other oxygen sensitive materials, and thereby increase shelf-life by decreasing oxygen in the headspace of the package, and decreasing oxidation of the packaged product.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Division of U.S. application Ser. No. 09/376,657,filed Aug. 18, 1999, now U.S. Pat. No. 6,569,506, and aContinuation-in-Part of U.S. application Ser. No. 09/141,168, filed Aug.27, 1998, now U.S. Pat. No. 6,333,087.

FIELD OF THE INVENTION

The present invention relates to oxygen scavenging for use in packaging,such as in gable-top or rectangular cartons used to package foodproducts, beverages, oxygen-sensitive materials and components.

BACKGROUND OF THE INVENTION

It is well known that regulating the exposure of oxygen-sensitiveproducts to oxygen maintains and enhances the quality and “shelf-life”of the product. For instance, by limiting the exposure of oxygensensitive food products to oxygen in a packaging system, the quality orfreshness of food is maintained, spoilage reduced, and the food shelflife extended. In the food packaging industry, several means forregulating oxygen exposure have already been developed. These meansinclude modified atmosphere packaging (MAP) and oxygen barrier filmpackaging.

For packaging material used in gable top or rectangular cartons, acoated paper or cardboard stock is often used. The coating for the paperor cardboard stock is usually a polymer-based resin, such aspolyethylene, which can be applied to the paper or paperboard stock byextrusion coating or laminating. Such a coating serves not only to makethe packaging material waterproof, but can also serve as an oxygenbarrier.

In one known example of such an extrusion coated paper packagingmaterial, the extrusion coating composition is comprised of greater than20 and less than 98 weight percent of a high pressure low densitypolyethylene homopolymer and/or copolymer and greater than 2 and lessthan 80 weight percent of at least one linear low density ethylenehydrocarbon copolymer.

In an example of such a resin coated packaging material specificallydesigned to have enhanced oxygen barrier qualities, an additional layerof polyamide is added to the low density polyethylene laminatedpaperboard. In a similar example, an additional layer of heat-sealableethylene vinyl alcohol copolymer is added to the low densitypolyethylene laminated paperboard.

One method currently being used for regulating oxygen exposure is“active packaging”, whereby the package containing the food product hasbeen modified in some manner to regulate the food's exposure to oxygen.One form of active packaging uses oxygen-scavenging sachets whichcontain a composition which scavenges the oxygen through oxidationreactions. One type of sachet contains iron-based compositions whichoxidize to their ferric states. Another type of sachet containsunsaturated fatty acid salts on a particulate adsorbent. Yet anothersachet contains metal/polyamide complex. However, one disadvantage ofsachets is the need for additional packaging operations to add thesachet to each package. A further disadvantage arising from theiron-based sachets is that certain atmospheric conditions (e.g., highhumidity, low CO₂ level) in the package are sometimes required in orderfor scavenging to occur at an adequate rate. Further, the sachets canpresent a problem to consumers if accidentally ingested.

Another means for regulating exposure of a packaged product to oxygeninvolves incorporating an oxygen scavenger into the packaging structureitself. A more uniform scavenging effect through the package is achievedby incorporating the scavenging material in the package instead ofadding a separate scavenger structure (e.g., a sachet) to the package.This may be especially important where there is restricted airflowinside the package. In addition, incorporating the oxygen scavenger intothe package structure provides a means of intercepting and scavengingoxygen as it permeates the walls of the package (herein referred to asan “active oxygen barrier”), thereby maintaining the lowest possibleoxygen level in the package. Limited success has been achieved inincorporating oxygen scavenging material into the walls of packages forvarious types of food.

One attempt to prepare an oxygen-scavenging wall involves theincorporation of inorganic powders and/or salts. However, incorporationof these powders and/or salts causes reduction of the wall's opticaltransparency, discoloration after oxidation, and reduced mechanicalproperties such as tear strength. In addition, these compounds can leadto processing difficulties, especially when fabricating thin films. Theoxidation products, which can be absorbed by food in the container,typically would not have FDA approval for human consumption.

Some oxygen scavenging systems produce an oxygen-scavenging wall. Thisis done by incorporating a metal catalyst-polyamide oxygen scavengingsystem into the package wall. Through catalyzed oxidation of thepolyamide, the package wall regulates the amount of oxygen which reachesthe interior volume of the package (active oxygen barrier) and has beenreported to have oxygen scavenging rate capabilities up to about 5 cubiccentimeters (cc) oxygen per square meter per day at ambient conditions.However, this system suffers from significant disadvantages.

One particularly limiting disadvantage of polyamide/catalyst materialscan be a low oxygen scavenging rate. Adding these materials to ahigh-barrier package containing air can produce a package which is notgenerally suitable for creating the desired internal oxygen level.

There are also disadvantages to having the oxygen-scavenging groups inthe backbone or network structure in this type of polyamide polymer. Thebasic polymer structure can be degraded and weakened upon reaction withoxygen. This can adversely affect physical properties such as tensile orimpact strength of the polymer. The degradation of the backbone ornetwork of the polymer can further increase the permeability of thepolymer to those materials sought to be excluded, such as oxygen.

Moreover, polyamides previously used in oxygen scavenging materials,such as MXD6, are typically incompatible with thermoplastic polymersused in most plastic packaging walls, such as ethylene-vinyl acetatecopolymers and low density polyethylene. Even further, when suchpolyamides are used by themselves to make a package wall, they mayresult in inappropriately stiff structures. They also incur processingdifficulties and higher costs when compared with the costs ofthermoplastic polymers typically used to make flexible packaging. Evenfurther, they are difficult to heat seal. Thus, all of these are factorsto consider when selecting materials for packages, especiallymulti-layer flexible packages and when selecting systems for reducingoxygen exposure of packaged products.

Another approach to scavenging oxygen is an oxygen-scavengingcomposition comprising an ethylenically unsaturated hydrocarbon and atransition metal catalyst. Ethylenically unsaturated compounds such assqualene, dehydrated castor oil, and 1,2-polybutadiene are useful oxygenscavenging compositions, and ethylenically saturated compounds such aspolyethylene and ethylene copolymers are useful as diluents.Compositions utilizing squalene, castor oil, or other such unsaturatedhydrocarbon typically have an oily texture as the compound migratestoward the surface of the material. Further, polymer chains which areethylenically unsaturated in the backbone would be expected to degradeupon scavenging oxygen, weakening the polymer due to polymer backbonebreakage, and generating a variety of off-odor, off-taste by-products.

Oxygen scavenging layers extruded or laminated onto the surface ofpaperboard stock have been tried with limited success. In one of theseexamples, the oxygen scavenging layer is an ethylenically unsaturatedhydrocarbon and a transition metal catalyst. Other known examples of anoxygen scavenging layer that can be coated onto the surface of paperboard stock and which furthermore retain oxygen scavenging capabilitiesat low temperatures are atactic-1,2-polybutadiene, EPDM rubbers,polyoctenamer, and 1,4-polybutadiene.

An oxygen-scavenging composition comprising a blend of a first polymericcomponent comprising a polyolefin is known, the first polymericcomponent having been grafted with an unsaturated carboxylic anhydrideor an unsaturated carboxylic acid, or combinations thereof, or with anepoxide; a second polymeric component having —OH, —SH, or —NHR² groupswhere R² is H, C₁-C₃ alkyl, substituted C₁-C₃ alkyl; and a catalyticamount of metal salt capable of catalyzing the reaction between oxygenand the second polymeric component, the polyolefin being present in anamount sufficient so that the blend is non phase-separated. A blend ofpolymers is utilized to obtain oxygen scavenging, and the secondpolymeric component is preferably a polyamide or a copolyamide such asthe copolymer of m-xylylene-diamine and adipic acid (MXD6).

Other oxidizable polymers recognized in the art include “highly active”oxidizable polymers such as poly(ethylene-methyl acrylate-benzylacrylate), EBZA, and poly(ethylene-methyl acrylate-tetrahydrofurylacrylate), EMTF, as well as poly(ethylene-methyl acrylate-nopolacrylate), EMNP. Blends of suitable polymers are also acceptable, suchas a blend of EMTF and poly-d-limonene. Although effective as oxygenscavengers, these polymers have the drawback of giving off a strong odorbefore oxygen scavenging and large amounts of volatile byproducts beforeand after oxygen scavenging.

Also known are oxygen-scavenging compositions which comprise atransition-metal salt and a compound having an ethylenic orpolyethylenic backbone and having allylic pendent or terminal moietieswhich contain a carbon atom that can form a free radical that isresonance-stabilized by an adjacent group. Such a polymer needs tocontain a sufficient amount and type of transition metal salt to promoteoxygen scavenging by the polymer when the polymer is exposed to anoxygen-containing fluid such as air. Although effective as oxygenscavengers, upon oxidation, it has been found that allylic pendentgroups on an ethylenic or polyethylenic backbone tend to generateconsiderable amounts of organic fragments. It is believed that this is aresult of oxidative cleavage. These fragments can interfere with the useof allylic pendent groups as oxygen scavengers in food packaging bygenerating compounds that can affect taste and odor of the packagedproducts.

The present invention solves many of the problems of the prior artencountered when oxygen scavenging material has been incorporated intopackaging materials. In various specific embodiments, the presentinvention solves many of the particular problems encountered withincorporating oxygen scavenging material into the structure of foodpackaging material such as paperboard stock for gable-top or rectangularcartons.

SUMMARY OF THE INVENTION

In one embodiment, the present invention relates to a method of usingoxygen scavenging material to decrease oxidation and maintain productproperties in packaged beverages, foods, oxygen sensitive materials oroxygen sensitive components comprising the steps of:

-   -   (a) incorporating an oxygen scavenging material into the        structure of a container used to package beverages, foods,        oxygen sensitive materials or oxygen sensitive components;    -   (b) placing beverages, foods, oxygen sensitive materials or        oxygen sensitive components in the container;    -   (c) sealing the container; and    -   (d) storing the container at a temperature between 20° F. and        120° F.;        wherein the oxygen scavenging material is selected from the        group consisting of oxidizable polymers, ethylenically        unsaturated polymers, benzylic polymers, allylic polymers,        polybutadiene, poly[ethylene-methyl acrylate-cyclohexene        acrylate] terpolymers, poly[ethylene-vinylcyclohexene]        copolymers, polylimonene resins, poly β-pinene, poly α-pinene        and a combination of a polymeric backbone, cyclic olefinic        pendent groups and linking groups linking the olefinic pendent        groups to the polymeric backbone.

The foregoing embodiment is particularly applicable to gable top orrectangular cartons particularly when they contain a juice such asorange juice. It has been found that the most preferred oxygenscavenging material is a combination of a polymeric backbone, cyclicolefinic pendent groups and linking groups linking the olefinic pendentgroups to the polymeric backbone.

In another embodiment, the invention relates to a method of storingbeverages, foods, oxygen-sensitive materials or oxygen-sensitivecomponents for an extended period while maintaining product propertiescomprising the steps of:

-   -   (a) incorporating an oxygen scavenging material into the        structure of a container used to package beverages, foods,        oxygen-sensitive materials or oxygen-sensitive components;    -   (b) placing beverages, foods, oxygen sensitive materials or        oxygen sensitive components in the container;    -   (c) sealing the container; and    -   (d) storing the container at a temperature between 20° F. and        120° F.;        wherein the oxygen scavenging material is selected from the        group consisting of oxidizable polymers, ethylenically        unsaturated polymers, benzylic polymers, allylic polymers,        polybutadiene, poly[ethylene-methyl acrylate-cyclohexene        acrylate] terpolymers, poly[ethylene-vinylcyclohexene]        copolymers, polylimonene resins, poly β-pinene, poly α-pinene        and a combination of a polymeric backbone, cyclic olefinic        pendent groups and linking groups linking the olefinic pendent        groups to the polymeric backbone.

The foregoing embodiment is particularly applicable to gable top orrectangular cartons particularly when they contain a juice such asorange juice. It has been found that the most preferred oxygenscavenging material is a combination of a polymeric backbone, cyclicolefinic pendent groups and linking groups linking the olefinic pendentgroups to the polymeric backbone.

In yet another embodiment, the present invention relates to a rigidpaperboard container, the container being constructed from extrusioncoated or laminated paperboard comprising:

-   -   (a) a paperboard substrate having opposed inner and outer        surfaces;    -   (b) a first polymer layer coated or laminated onto the outer        surface of said paperboard substrate; and    -   (c) an inner, product contact sandwich layer comprising an        oxygen barrier layer and an oxygen scavenging layer;        wherein the oxygen scavenging material is selected from the        group consisting of oxidizable polymers, ethylenically        unsaturated polymers, benzylic polymers, allylic polymers,        polybutadiene, poly[ethylene-methyl acrylate-cyclohexene        acrylate] terpolymers, poly[ethylene-vinylcyclohexene]        copolymers, polylimonene resins, poly β-pinene, poly α-pinene        and a combination of a polymeric backbone, cyclic olefinic        pendent groups and linking groups linking the olefinic pendent        groups to the polymeric backbone.

The foregoing embodiment is particularly applicable to gable top orrectangular cartons particularly when they contain a juice such asorange juice. It has been found that the most preferred oxygenscavenging material to use is a combination of a polymeric backbone,cyclic olefinic pendent groups and linking groups linking the olefinicpendent groups to the polymeric backbone.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the measured vitamin C retention in orangejuice packaged in glass container, PBL and OS cartons as described inExample 1. The graph is plotted as mg/liter vitamin C vs. time.

FIG. 2 is a graph showing the measured dissolved oxygen in orange juicepackaged in glass container, PBL and OS cartons as described inExample 1. The graph is plotted as mg/liter oxygen vs. time.

FIG. 3 is a graph showing the measured vitamin C retention in orangejuice packaged in OS and PBL cartons with OS films as described inExample 1. The graph is plotted as mg/liter vitamin C vs. time.

FIG. 4 is a graph showing the measured dissolved oxygen in OS and PBLcartons with OS films as described in Example 1. The graph is plotted asmg/liter oxygen vs. time.

DETAILED DESCRIPTION OF THE INVENTION

The oxygen scavenging system of the present invention has a number ofbenefits including, but not limited to: extending shelf life; preservingproduct color; improving taste and odor; reducing mold growth; andretaining vitamin and other nutritional value.

Because these scavengers are actually part of the package, theyeliminate the additional handling steps and safety concerns associatedwith oxygen scavenging sachets. In fact, the oxygen scavenging system ofthe present invention could be incorporated into an existing packagingstructure without any consumer awareness of change in the packageappearance.

The oxygen scavenging polymers can be incorporated into a layer of afilm or rigid package using standard extrusion equipment. Because thescavenger material permeates an entire layer incorporated into thepackage wall, the capacity per cost of scavenger compares very favorablyto systems where the scavenger is added into the package wall in somefashion.

This invention relates to the use of oxygen scavengers in packagingmaterials, for example, extrusion-coated, rigid containers. In a morespecific embodiment, the containers are in the form of gable top andrectangular cartons, for beverages, foods, and other oxygen sensitivematerials and components. A non-limiting list of possible productsinclude fruit juices, prepared foods, snack foods, as well as otheroxygen-sensitive materials such as chemicals and oxygen-sensitivecomponents, such as computer parts.

The containers in the present invention can be filled under eitheraseptic packaging conditions or under cold-filled packaging conditions,without the specific procedures used for aseptic packaging conditions(which is how the samples discussed in the Examples are prepared).

A non-limiting description of a typical procedure used for asepticpackaging conditions for carton containers is as follows. The packagingmaterials are formed into cartons and sterilized in the filler machinewith hot hydrogen peroxide vapor. Once the vapor is evaporated with hot,sterile air or ultraviolet light, the sterilized package is filled atambient temperature with the sterilized product and then sealed within asterile zone.

By incorporating an oxygen scavenging layer as an inner layer in thewalls of the packaging material or as a strip attached somewhere on theinner surface of the packaging material, oxidation of productproperties, such as the nutritional value in beverages or foods, isreduced significantly.

In a preferred embodiment, the oxygen scavengers are combined with atransition-metal salt to catalyze the oxygen scavenging properties ofthe materials. A transition-metal salt, as the term is used here,comprises an element chosen from the first, second and third transitionseries of the periodic table of the elements, particularly one that iscapable of promoting oxygen scavenging. This transition-metal salt is ina form, which facilitates or imparts scavenging of oxygen by thecomposition of this invention. A plausible mechanism, not intended toplace limitations on this invention, is that the transition element canreadily inter-convert between at least two oxidation states andfacilitates formation of free radicals. Suitable transition-metalelements include, but are not limited to, manganese II or III, iron IIor III, cobalt II or III, nickel II or III, copper I or II, rhodium II,III or IV, and ruthenium. The oxidation state of the transition-metalelement when introduced into the composition is not necessarily that ofthe active form. It is only necessary to have the transition-metalelement in its active form at or shortly before the time that thecomposition is required to scavenge oxygen. The transition-metal elementis preferably iron, nickel or copper, more preferably manganese, andmost preferably cobalt.

Suitable counter-ions for the transition metal element are organic orinorganic anions. These include, but are not limited to, chloride,acetate, stearate, oleate, palmitate, 2-ethylhexanoate, citrate,glycolate, benzoate, neodecanoate or naphthenate. Organic anions arepreferred. Particularly preferable salts include cobalt2-ethylhexanoate, cobalt benzoate, cobalt stearate, cobalt oleate andcobalt neodecanoate. The transition-metal element may also be introducedas an ionomer, in which case a polymeric counter-ion is employed.

The composition of the present invention when used in forming an oxygenscavenging packaging article can be composed solely of theabove-described polymer and transition metal catalyst. However,components, such as photoinitiators, can be added to further facilitateand control the initiation of oxygen scavenging properties. Forinstance, it is often preferable to add a photoinitiator, or a blend ofdifferent photoinitiators, to the oxygen scavenger compositions,especially when antioxidants are included to prevent premature oxidationof that composition during processing.

Suitable photoinitiators are well known in the art. Such photoinitiatorsare discussed in U.S. patent application Ser. No. 08/857,325 in whichsome of the present inventors were contributing inventors and which isincorporated herein by reference. Specific examples include, but are notlimited to, benzophenone, o-methoxy-benzophenone, acetophenone,o-methoxy-acetophenone, acenaphthenequinone, methyl ethyl ketone,valerophenone, hexanophenone, α-phenyl-butyrophenone,p-morpholinopropiophenone, dibenzosuberone, 4-morpholinobenzophenone,benzoin, benzoin methyl ether, 4-o-morpholinodeoxybenzoin,p-diacetylbenzene, 4-aminobenzophenone, 4′-methoxyacetophenone,substituted and unsubstituted anthraquinones, α-tetralone,9-acetylphenanthrene, 2-acetylphenanthrene, 10-thioxanthenone,3-acetyl-phenanthrene, 3-acetylindole, 9-fluorenone, 1-indanone,1,3,5-triacetylbenzene, thioxanthen-9-one, xanthene-9-one,7-H-benz[de]anthracen-7-one, benzoin tetrahydropyranyl ether,4,4′-bis(dimethylamino)-benzophenone, 1′-acetonaphthone,2′-acetonaphthone, acetonaphthone and 2,3-butanedione,benz[a]anthracene-7,12-dione, 2,2-dimethoxy-2-phenylacetophenone,α,α-diethoxy-acetophenone, α,α-dibutoxyacetophenone, etc. Singlet oxygengenerating photosensitizers such as Rose Bengal, methylene blue, andtetraphenyl porphine may also be employed as photoinitiators. Polymericinitiators include polyethylene carbon monoxide andoligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone]. Use of aphotoinitiator is preferable because it generally provides faster andmore efficient initiation. When actinic radiation is used, theinitiators may also provide initiation at longer wavelengths which areless costly to generate and less harmful.

When a photoinitiator is used, its primary function is to enhance andfacilitate the initiation of oxygen scavenging upon exposure toradiation. The amount of photoinitiator can vary. In many instances, theamount will depend on the amount and type of monomers present in thepresent invention, the wavelength and intensity of radiation used, thenature and amount of antioxidants used, as well as the type ofphotoinitiator used. The amount of photoinitiator also depends on howthe scavenging composition is used. For instance, if thephotoinitiator-coating composition is placed underneath a layer, whichis somewhat opaque to the radiation used, more initiator may be needed.For most purposes, however, the amount of photoinitiator, when used,will be in the range of 0.01 to 10% by weight of the total composition.The initiating of oxygen scavenging can be accomplished by exposing thepackaging article to actinic or electron beam radiation, as describedbelow.

Antioxidants may be incorporated into the scavenging compositions usedin this invention to control degradation of the components duringcompounding and shaping. An antioxidant, as defined herein, is anymaterial, which inhibits oxidative degradation or cross-linking ofpolymers. Typically, such antioxidants are added to facilitate theprocessing of polymeric materials and/or prolong their useful lifetime.

Antioxidants such as Vitamin E, Irganox® 1010,2,6-di(t-butyl)4-methyl-phenol(BHT),2,2′-methylene-bis(6-t-butyl-p-cresol), triphenylphosphite,tris-(nonylphenyl)phosphite and dilaurylthiodipropionate would besuitable for use with this invention.

When an antioxidant is included as part of the packaging, it should beused in amounts which will prevent oxidation of the scavengercomposition's components as well as other materials present in aresultant blend during formation and processing but the amount should beless than that which would interfere with the scavenging activity of theresultant layer, film or article after initiation has occurred. Theparticular amount needed will depend on the particular components of thecomposition, the particular antioxidant used, the degree and amount ofthermal processing used to form the shaped article, and the dosage andwavelength of radiation applied to initiate oxygen scavenging and can bedetermined by conventional means. Typically, they are present in about0.01 to 1% by weight.

Other additives which may also be included in oxygen scavenger layersinclude, but are not necessarily limited to, fillers, pigments,dyestuffs, stabilizers, processing aids, plasticizers, fire retardants,anti-fog agents, etc.

The amounts of the components which are used in the oxygen scavengingcompositions, or layers have an effect on the use, effectiveness andresults of this method. Thus, the amounts of polymer, transition metalcatalyst and any photoinitiator, antioxidant, polymeric diluents andadditives, can vary depending on the article and its end use.

For instance, one of the primary functions of the polymer describedabove is to react irreversibly with oxygen during the scavengingprocess, while the primary function of the transition metal catalyst isto facilitate this process. Thus, to a large extent, the amount ofpolymer present will affect the oxygen scavenging capacity of thecomposition, i.e., affect the amount of oxygen that the composition canconsume. The amount of transition metal catalyst will affect the rate atwhich oxygen is consumed. Because it primarily affects the scavengingrate, the amount of transition metal catalyst may also affect theinduction period.

Any further additives employed normally will not comprise more than 10%of the scavenging composition, with preferable amounts being less than5% by weight of the scavenging composition.

Optionally, the methods of this invention can include exposure of thepolymer containing the oxygen scavenging-promoting transition metalcatalyst to actinic radiation to reduce the induction period, if any,before oxygen scavenging commences. A method is known for initiatingoxygen scavenging by exposing a film comprising an oxidizable organiccompound and a transition metal catalyst to actinic radiation. Suchmethods are discussed in U.S. Pat. No. 5,211,875, the disclosure ofwhich patent is incorporated herein by reference. A composition of thepresent invention which has a long induction period in the absence ofactinic radiation but a short or non-existent induction period afterexposure to actinic radiation is particularly preferred. Compositionswhich are activated by actinic radiation can be stored without specialpreparation or storage requirements, such as being packaged or kept in anitrogen environment. They maintain a high capability for scavengingoxygen upon activation with actinic radiation. Thus, oxygen scavengingcan be activated when desired.

The radiation used in this method could be light, e.g., ultraviolet orvisible light having a wavelength of about 200 to 750 nanometers (nm),and preferably having a wavelength of about 200 to 600 nm, and mostpreferably from about 200 to 400 nm. When employing this method, it ispreferable to expose the oxygen scavenger to at least 1 Joule per gramof scavenging composition. A typical amount of exposure is in the rangeof 10 to 2000 Joules per gram. The radiation can also be an electronbeam radiation at a dosage of about 2 to 200 kiloGray, preferably about10 to 100 kiloGray. Other sources of radiation include ionizingradiation such as gamma, X-rays and corona discharge. The duration ofexposure depends on several factors including, but not limited to, theamount and type of photoinitiator present, thickness of the layers to beexposed, thickness and opacity of intervening layers, amount of anyantioxidant present, and the wavelength and intensity of the radiationsource. The radiation provided by heating of polyolefin and the likepolymers (e.g., 100-250° C.) during processing does not enabletriggering to take effect.

In various specific embodiments, the use of oxygen-scavengingcompositions in the present invention can be accomplished by coatingoxygen scavenging composition onto materials such as metallic foil,polymer film, metallized film, paper or cardboard to provide oxygenscavenging properties. The compositions are also useful in makingarticles such as single or multi-layer rigid thick-walled plasticcontainers or bottles (typically, between 8 and 100 mils in thickness)or in making single or multi-layer flexible films, especially thin films(less than 3 mil, or even as thin as about 0.25 mil). Some of thecompositions of the present invention are easily formed into films usingwell-known means. These films can be used alone or in combination withother films or materials.

The compositions used in the present invention may be further combinedwith one or more polymers, such as thermoplastic polymers which aretypically used to form film layers in plastic packaging articles. In themanufacture of certain packaging articles, well-known thermosets canalso be used as a polymeric diluent.

Selecting combinations of a diluent and the composition used in thepresent invention depends on the properties desired. Polymers which canbe used as the diluent include, but are not limited to, polyethylene,low or very low density polyethylene, polypropylene, polyvinyl chloride,and ethylene copolymers such as ethylene-vinyl acetate, ethylene-alkylacrylates or methacrylates, ethylene-acrylic acid or methacrylic acid,and ethylene-arylic or methacrylic acid ionomers. In rigid packagingapplications, polystyrene is used; and in rigid articles such asbeverage containers, polyethylene terephthalate (PET) is often used.Blends of different diluents may also be used. However, as indicatedabove, the selection of the polymeric diluent largely depends on thearticle to be manufactured and the end use. Such selection factors arewell known in the art.

If a diluent polymer such as a thermoplastic is employed, it shouldfurther be selected according to its compatibility with the compositionof the present invention. In some instances, the clarity, cleanliness,effectiveness as an oxygen-scavenger, barrier properties, mechanicalproperties and/or texture of the article can be adversely affected by ablend containing a polymer which is incompatible with the composition ofthe present invention.

A blend of a composition used in the present invention with a compatiblepolymer can be made by dry blending or by melt-blending the polymerstogether at a temperature in the approximate range of 50° C. to 250° C.Alternative methods of blending include the use of a solvent followed byevaporation. When making film layers or articles from oxygen-scavengingcompositions, extrusion or coextrusion, solvent casting, injectionmolding, stretch blow molding, orientation, thermoforming, extrusioncoating, coating and curing, lamination or combinations thereof wouldtypically follow the blending.

Layers in the package wall of the present invention may be in severalforms. They may be in the form of stock films, including “oriented” or“heat shrinkable” films, which may ultimately be processed as bags,etc., or in the form of stretch-wrap films. The layers may also be inthe form of sheet inserts to be placed in a packaging cavity. In apreferred embodiment of a rigid paperboard beverage container, the layermay be within the container's walls. Even further, the layer may also bein the form of a liner placed with or in the container's lid or cap. Thelayer may even be coated or laminated onto any one of the articlesmentioned above.

In multi-layered articles, the scavenging layer used in the presentinvention may be included with layers such as, but not necessarilylimited to, “oxygen barriers”, i.e., a layer of material having anoxygen transmission rate equal to or less than 500 cubic centimeters persquare meter (cc/m²) per day per atmosphere at room temperature, i.e.about 25° C. Typical oxygen barriers are poly(ethylene vinyl alcohol)(“EVOH”), polyacrylonitrile, polyvinyl chloride, poly(vinylidenedichloride), polyethylene terephthalate, silica, and polyamides. Metalfoil layers can also be employed.

The polyvinylchloride (“PVC”) and poly(vinylidene dichloride) (“PVDC”)materials include normally crystalline polymers, both homopolymers andcopolymers, containing vinylidene chloride. Copolymerizable materialssuch as vinyl chloride, acrylonitrile, vinyl acetate, ethyl acrylate,ethyl methacrylate and methyl methacrylate can be used. Terpolymers canalso be employed, e.g., a terpolymer of vinylidene chloride, dimethylmaleate and vinyl chloride.

The term “polyamide” refers to high molecular weight polymers havingamide linkages along the molecular chain, and refers more specificallyto synthetic polyamide such as various Nylons such as Nylon 6, 66, 6/12,6/66 and 6/69, including high density versions and nylon copolymers.

To determine the oxygen scavenging capabilities of a composition, therate of oxygen scavenging can be calculated by measuring the time thatelapsed before the article depletes a certain amount of oxygen from asealed container. For instance, a film comprising the scavengingcomponent can be placed in an air-tight, sealed container of a certainoxygen containing atmosphere, e.g., air which typically contains 20.9%oxygen by volume. Then, over a period of time, samples of the atmosphereinside the container are removed to determine the percentage of oxygenremaining. The scavenging rates of the compositions and layers used inthe present invention will change with changing temperature andatmospheric conditions.

When an active oxygen barrier is prepared, the scavenging rate can be aslow as 0.1 cc oxygen per gram of composition of the present inventionper day in air at 25° C. and 1 atmosphere pressure. However, preferablecompositions of this invention have rates equal to or greater than 1 ccoxygen per gram per day, thus making them suitable for scavenging oxygenfrom within a package, as well as suitable for active oxygen barrierapplications. Many compositions are even capable of more preferablerates equal to or greater than 5.0 cc O₂ per gram per day.

In an active oxygen barrier application, it is preferable that thecombination of oxygen barriers and any oxygen scavenging activity createan overall oxygen transmission rate of less than about 1.0 cubiccentimeter-mil per square meter per day per atmosphere pressure at 25°C. Another definition of acceptable oxygen scavenging is derived fromtesting actual packages. In actual use, the scavenging rate requirementwill largely depend on the internal atmosphere of the package, thecontents of the package and the temperature at which it is stored.

In a packaging article made according to this invention, the scavengingrate will depend primarily on the amount and nature of the compositionof the present invention in the article, and secondarily on the amountand nature of other additives (e.g., diluent polymer, antioxidant, etc.)which are present in the scavenging component, as well as the overallmanner in which the package is fabricated, e.g., surface area/volumeratio.

The oxygen scavenging capacity of an article comprising the inventioncan be measured by determining the amount of oxygen consumed until thearticle becomes ineffective as a scavenger. The scavenging capacity ofthe package will depend primarily on the amount and nature of thescavenging moieties present in the article, as discussed above.

In actual use, the oxygen scavenging capacity requirement of the articlelargely depends on three parameters of each application:

-   -   (1) the quantity of oxygen initially present in the package;    -   (2) the rate of oxygen entry into the package in the absence of        the scavenging property; and    -   (3) the intended shelf life for the package.

The scavenging capacity of the composition can be as low as 1 cc oxygenper gram, but is preferably at least 10 cc oxygen per gram, and morepreferably at least 50 cc oxygen per gram. When such compositions are ina layer, the layer will preferably have an oxygen capacity of at least250 cc oxygen per square meter per mil thickness and more preferably atleast 500 cc oxygen per square meter per mil thickness.

In a preferred embodiment, the present invention relates to a rigidpaperboard container which is constructed from extrusion coated orlaminated paperboard. The paperboard container comprises a paperboardsubstrate with opposed inner and outer surfaces, the inner surface beingthe side of the paperboard substrate which has contact with the airinside the container and the outer surface being the side of thepaperboard substrate which has contact with the air outside thecontainer.

The outer surface of the paperboard substrate is coated or laminatedwith at least one polymer layer and the inner surface of the paperboardsubstrate is coated with at least an oxygen barrier layer and an oxygenscavenging layer. The polymer layer can be low density polyethylenepolymer, linear low density polyethylene polymer, a blend of low densitypolyethylene polymer and linear low density polyethylene polymer, or acoextrusion of low density polyethylene polymer and linear low densitypolyethylene polymer. The oxygen barrier layer can be, among otherthings, metallized film, such as foil, ethylene vinyl alcohol (EVOH) orpolyamides.

In one embodiment of the inner surface of the above-described invention,there is at least one adhesive tie layer adjacent to the oxygen barrierlayer. Adhesive tie layers may be made of various polymeric adhesives,especially anhydride grafted polymers, copolymers or terpolymers as wellas maleic anhydride and rubber modified polymers. In another embodimentof the above-described embodiment of the invention, an adhesive tielayer is juxtaposed between the barrier layer and the polymer layercoated or laminated onto the inner surface of the paperboard substrate.In a more preferred embodiment of the tie layer, the materials used areionomers, specifically zinc ionomers or sodium ionomers. In another morepreferred embodiment of the above-described embodiments of theinvention, the tie layer of the inner, product contact, sandwich layercomprises ethylene acrylic acid. In another more preferred embodiment,the tie layer of the inner product contact sandwich layer comprisesethylene methacrylic acid.

In another preferred embodiment of the above-described embodiment of theinvention, the inner product contact sandwich layer further comprises apolymer layer coating or laminating the innermost surface of the innerproduct contact sandwich layer. The polymer layer can be low densitypolyethylene polymer, linear low density polyethylene polymer, a blendof low density polyethylene polymer and linear low density polyethylenepolymer, or a coextrusion of low density polyethylene polymer and linearlow density polyethylene polymer.

In another preferred embodiment of the above-described embodiment of theinvention, a second polymer layer is coated or laminated onto the innersurface of the paperboard substrate. This second polymer layer can below density polyethylene polymer, linear low density polyethylenepolymer, a blend of low density polyethylene polymer and linear lowdensity polyethylene polymer, and a coextrusion of low densitypolyethylene polymer and linear low density polyethylene polymer.

In yet another preferred embodiment of the above-described embodiment ofthe invention, a third polymer layer is coated or laminated onto theinner surface of the oxygen scavenging layer of the inner, productcontact, sandwich layer. This third polymer layer can be low densitypolyethylene polymer, linear low density polyethylene polymer, a blendof low density polyethylene polymer and linear low density polyethylenepolymer, and a coextrusion of low density polyethylene polymer andlinear low density polyethylene polymer.

In still another preferred embodiment of the above-described embodimentof the invention, the inner product contact sandwich layer furthercomprises a fourth polymer layer and a second oxygen scavenging layer,the second oxygen scavenging layer being on the inner surface of thethird polymer layer and the fourth polymer layer coating or laminatingthe inner surface of the second oxygen scavenging layer. This secondpolymer layer can be low density polyethylene polymer, linear lowdensity polyethylene polymer, a blend of low density polyethylenepolymer and linear low density polyethylene polymer, and a coextrusionof low density polyethylene polymer and linear low density polyethylenepolymer.

In yet another preferred embodiment of the above-described embodiment ofthe invention, a tie layer is coated or laminated onto the inner surfaceof the oxygen scavenging layer and an ethylene vinyl alcohol layer iscoated or laminated onto the inner surface of the tie layer coating orlaminating the inner surface of the oxygen scavenging layer.

In still another preferred embodiment of the above-described embodimentof the invention, the inner product contact sandwich layer furthercomprises a second barrier layer and a second tie layer, the secondbarrier layer being on the inner surface of the first tie layer and thesecond tie layer being juxtaposed between the inner surface of thesecond barrier layer and the outer surface of the oxygen scavenginglayer.

In a more preferred embodiment of the above-described embodiments of theinvention, the oxygen scavenging material is selected from the groupconsisting of oxidizable polymers, ethylenically unsaturated polymers,benzylic polymers, allylic polymers, polybutadiene, poly[ethylene-methylacrylate-cyclohexene acrylate] terpolymers,poly[ethylene-vinylcyclohexene] copolymers, polylimonene resins, polyβ-pinene and poly α-pinene.

In a more preferred embodiment of the above-described embodiments of theinvention, the oxygen scavenging material of either of the above methodscomprises a polymeric backbone, cyclic olefinic pendent groups andlinking groups linking the olefinic pendent groups to the polymericbackbone.

In a more preferred embodiment of the above-described embodiments of theinvention, the polymeric backbone is ethylenic and the linking groupsare selected from the group consisting of:—O—(CHR)_(n)—; —(C═O)—O—(CHR)_(n)—; —NH—(CHR)_(n)—; —O—(C═O)—(CHR)_(n)—;—(C═O)—NH—(—CHR)_(n)—; and —(C═O)—O—CHOH—CH₂—O—;wherein R is hydrogen or an alkyl group selected from the groupconsisting of methyl, ethyl, propyl and butyl groups and where n is aninteger in the range from 1 to 12.

In a more preferred embodiment of the above-described embodiments of theinvention, the cyclic olefinic pendent groups have the structure (I):

where q₁, q₂, q₃, q₄, and r are selected from the group consisting of—H, —CH₃, and —C₂H₅; and where m is —(CH₂)_(n)— with n being an integerin the range from 0 to 4; and wherein, when r is —H, at least one of q₁,q₂, q₃ and q₄ is —H.

In a more preferred embodiment of the above-described embodiments of theinvention, the polymeric backbone comprises monomers selected from thegroup consisting of ethylene and styrene.

Other factors may also affect oxygen scavenging and should be consideredwhen selecting compositions. These factors include but are not limitedto temperature, relative humidity, and the atmospheric environment inthe package.

The oxygen scavenging materials of the present invention are capable ofaltering the composition of the gases within the headspace of a package.The resulting advantage is an enhanced shelf life of food products. Inone embodiment, the oxygen scavenger is incorporated as a layer in apolymer coated paperboard substrate material used to form a gable topcarton for juice beverages.

If the oxygen scavenger layer is used in such a polymer coatedpaperboard substrate material, formulation design may include, but notbe limited to, coated substrate materials with the following structures:

-   -   (A) Polymer Coating Layer (LDPE/LLDPE)/Paperboard        Substrate/Polymer Coating Layer/Barrier Layer (Metal Foil)/Tie        Layer (Ethylene Acrylic Acid or Zinc Ionomer)/Oxygen Scavenging        Layer/Polymer Coating Layer;    -   (B) Polymer Coating Layer/Paperboard Substrate/Polymer Coating        Layer/Tie Layer/Barrier Layer/Tie Layer/Oxygen Scavenging        Layer/Polymer Coating Layer;    -   (C) Polymer Coating Layer/Paperboard Substrate/Polymer Coating        Layer/Barrier Layer (Foil or Nylon)/Oxygen Scavenging        Layer/Polymer Coating Layer;    -   (D) Polymer Coating Layer/Paperboard Substrate/Polymer Coating        Layer/Tie Layer/Barrier Layer (EVOH or Nylon)/Tie Layer/Barrier        Layer/Tie Layer/Oxygen Scavenging Layer/Polymer Coating Layer;    -   (E) Polymer Coating Layer/Paperboard Substrate/Barrier Layer        (Nylon)/Barrier Layer (EVOH)/Tie Layer/Oxygen Scavenging        Layer/Polymer Coating Layer;    -   (F) Polymer Coating Layer/Paperboard Substrate/Barrier Layer        (Nylon)/Tie Layer/Oxygen Scavenging Layer/Polymer Coating Layer;    -   (G) Polymer Coating Layer/Paperboard Substrate/Polymer Coating        Layer/Tie Layer/Barrier Layer (EVOH or Nylon)/Tie Layer/Oxygen        Scavenging Layer/Polymer Coating Layer;    -   (H) Polymer Coating Layer/Paperboard Substrate/Polymer Coating        Layer/Tie Layer/Barrier Layer/Tie Layer/Oxygen Scavenging        Layer/Tie Layer/Barrier Layer;    -   (I) Polymer Coating Layer/Paperboard Substrate/Polymer Coating        Layer/Tie Layer/Barrier Layer/Tie Layer/Oxygen Scavenging Layer;    -   (J) Polymer Coating Layer/Paperboard Substrate/Polymer Coating        Layer/Barrier Layer (Foil)/Tie Layer (Ethylene Acrylic Acid or        Zinc Ionomer)/Oxygen Scavenging Layer;    -   (K) Polymer Coating Layer/Paperboard Substrate/Barrier Layer        (Nylon)/Tie Layer/Oxygen Scavenging Layer; and    -   (L) Polymer Coating Layer/Paperboard Substrate/Polymer Coating        Layer/Tie Layer/Barrier Layer (EVOH or Nylon)/Tie Layer/Oxygen        Scavenging Layer/Polymer Coating Layer/Oxygen Scavenging        Layer/Polymer Coating Layer.

The foregoing embodiments are particularly applicable to gable top orrectangular cartons, particularly when they contain a juice such asorange juice. It has been found that the most preferred oxygenscavenging material to use is a combination of a polymeric backbone,cyclic olefinic pendent groups and linking groups linking the olefinicpendent groups to the polymeric backbone.

EXAMPLES

Experiments were performed with several kinds of orange juice containersto measure both the amount of oxygen in the headspace of the containersas well as the amount of oxygen dissolved in the juice and the amount ofascorbic acid contained in the juice over a period of six weeks.

Example 1

A six-week shelf life study was conducted with orange juice packaged incommercial paperboard barrier laminate (PBL) cartons and in experimentalcarton samples using laminated board stock containing oxygen scavengingpolymer in the inner layers of the cartons. PBL cartons consist of alaminated paperboard with a low density polyethylene coated on the outersurface of the paperboard and an oxygen barrier layer on the insidesurface of the paperboard. The experimental oxygen scavenging (OS)cartons consisted of the PBL carton with a three-layer oxygen scavengingfilm (ABA Structure: Polyethylene/oxygen scavengingpolymer/Polyethylene) further laminated on the inside surface of theoxygen barrier layer. PBL cartons containing loose strips of thethree-layer oxygen scavenging film were also used. The oxygen scavengingfilms were one of three sizes: 4″×3½″, 4″×7″, and 4″×14″.

The juice cartons were stored at 40° F. and the orange juice was testedfor ascorbic acid (vitamin C) and dissolved oxygen on a weekly basis.After six weeks, the orange juice packaged in the oxygen scavengercartons retained a significantly greater amount of vitamin C as comparedto the commercial PBL cartons.

Cartons were filled with orange juice and the amount of dissolved oxygenin the orange juice was measured using a YSI Dissolved Oxygen meter. Theamount of vitamin C was measured by a visual titration method usedextensively by the citrus industry, (AOAC Method, 1965, Official methodsof Analysis, p. 764).

Orange juice in glass bottles was used as the control. PBL cartons wereused as a standard. The oxygen scavenger laminate portion of the PBLcarton with oxygen scavenger laminate was extrusion coated and laterconverted into trial cartons.

The six packaging constructions filled with orange juice were:

-   -   (1) Glass—Control.    -   (2) PBL carton—Standard.    -   (3) PBL carton with oxygen scavenger laminate (OS).    -   (4) PBL carton with 4″×3½″ oxygen scavenger film strip (Film 3).    -   (5) PBL carton with 4″×7″ oxygen scavenger film strip (Film 4).    -   (6) PBL carton with 4″×14″ oxygen scavenger film strip (Film 5).

The oxygen scavenging cartons and films were exposed to ultra-violetlight to activate the oxygen scavenger. The rapid decrease of dissolvedoxygen in these cartons is noted in the data. The oxygen scavenger atday one, (week 0), had already begun to remove oxygen from the juice. Byweek one, the dissolved oxygen had dropped significantly and remainedlow throughout the study. This correlated with the retention of vitaminC in these cartons.

Agitation of the juice during filling increases the oxygen present insolution. The oxygen scavenger filmstrips, which were dropped into PBLcartons, were aggressive in removing oxygen from the orange juice butwere not as effective as the extruded OS cartons. This may be due to thelimited exposure and surface area of the strips in relation to thevolume of the orange juice.

Graphs have been separated into four groups for ease of interpretation:

-   -   FIG. 1) Vitamin C retention in glass container, PBL and OS        cartons.    -   FIG. 2) Amount of dissolved oxygen in glass, PBL and OS cartons.    -   FIG. 3) Vitamin C retention in OS carton and PBL cartons with OS        film strips.    -   FIG. 4) Dissolved oxygen in OS carton and PBL cartons with OS        film strips.

VITAMIN C DATA, MG/LITER WEEK GLASS PBL OS FILM 3 FILM 4 FILM 5 0 34.3434.27 34.54 34.54 33.85 34.73 1 33.67 33.06 34.86 33.37 33.42 34.86 232.37 30.75 34.33 33.35 33.35 34.08 3 31.24 29.58 32.21 31.34 31.0430.95 4 32.86 30.15 33.72 31.25 32.76 32.76 5 33.42 26.77 32.32 28.6829.8 30.42 6 32.96 24.76 31.36 27.28 27.67 28.16

TOTAL VITAMIN C LOSS AFTER SIX WEEKS GLASS PBL OS FILM 3 FILM 4 FILM 5 %3.8 27.2 9.1 20.9 18.3 18.7

DISSOLVED OXYGEN, MG/LITER WEEK GLASS PBL OS FILM 3 FILM 4 FILM 5 0.04.3 3.8 2.5 2.7 2.9 1.8 1.0 4.3 2.9 0.3 0.7 0.9 0.9 2.0 0.3 1.4 0.2 0.81.3 1.5 3.0 0.1 1.0 0.3 1.1 1.1 0.9 4.0 0.2 1.0 0.8 0.8 1.1 1.1 5.0 0.21.6 1.0 0.4 1.5 1.3 6.0 0.2 3.4 0.3 1.7 2.3 4.0

Nutritional labeling of the orange juice requires that the statedpercent of vitamin C be maintained through the out date posted on thecarton. Oxygen will cause vitamin C to oxidize resulting in a loss ofvitamin C. The purpose of the oxygen scavenger is to remove oxygen fromthe juice, from the package headspace, and any fugitive oxygen thatpermeates through the package wall. This action is accomplished by acatalyzed metal reaction of the scavenger polymer with oxygen. Theoxygen scavenging polymer used in this test was astyrene/butadiene/styrene-based oxygen scavenger containing 1000 ppm ofcobalt ion (as cobalt neodecanoate) and 1000 ppm of benzoylbiphenyl(BBP) photoinitiator.

Barrier films, such as polyamides used in PBL, slow the permeation rateof oxygen through the board structure, but do not remove the oxygen fromthe package headspace or contents. The oxygen scavenger works to removeresidual and/or fugitive oxygen present in the package contents.

These preliminary results indicate that this oxygen scavenging packageprovides superior results for the extension of orange juice shelf life.

Example 2 Organoleptic Tests

The organoleptics (negative effects on taste and odor) of the presentinvention were tested by comparing the taste of water and a fatty foodpackaged in an extrusion coated package having a layer of oxygenscavenging material incorporated as an internal layer of the packagematerial with water and a fatty food packaged in a control package ofidentical structure but without the oxygen scavenging layer. Triangletests with forced preferences were run using 28 trained panelists. Inall cases, the sensory panel results showed a statistically significant(P<0.0001) preference for the packages containing the oxygen scavengingsystem over the control.

Although a few embodiments of the invention have been described indetail above, it will be appreciated by those skilled in the art thatvarious modifications and alterations can be made to the particularembodiments shown without materially departing from the novel teachingsand advantages of the invention. Accordingly, it is to be understoodthat all such modifications and alterations are included within thespirit and scope of the invention as defined by the following claims.

1. A rigid paperboard container, the container being constructed fromextrusion coated or laminated paperboard comprising: (a) a paperboardsubstrate having opposed inner and outer surfaces; (b) a first polymerlayer coated or laminated onto the outer surface of said paperboardsubstrate, the first polymer layer comprising one or more materialsselected from the group consisting of i) low density polyethylenepolymer, ii) linear low density polyethylene polymer, iii) a blend oflow density polyethylene polymer and linear low density polyethylenepolymer, and iv) a coextrusion of low density polyethylene polymer andlinear low density polyethylene polymer; and (c) an inner productcontact sandwich layer comprising i) a second polymer layer coated orlaminated onto the inner surface of said paperboard substrate, ii) afirst tie layer, the first tie layer comprising one or more materialsselected from the group consisting of (a) anhydride grafted polymer,copolymer or terpolymer, (b) maleic anhydride modified polymer, and (c)ionomer; iii) an oxygen barrier layer comprising one or more materialsselected from the group consisting of (a) ethylene vinyl alcoholcopolymer, and (b) polyamide; iv) a second tie layer, the second tielayer comprising one or more materials selected from the groupconsisting of (a) anhydride grafted polymer, copolymer or terpolymer,(b) maleic anhydride modified polymer, and (c) ionomer; v) an oxygenscavenging layer comprising an oxygen scavenging material; wherein theoxygen scavenging material is selected from the group consisting of (a)poly[ethylene-methyl acrylate-cyclohexene acrylate] terpolymer and atransition metal catalyst, (b) a combination of a polymeric backbone,cyclic olefinic pendent groups and linking groups linking the olefinicpendent groups to the polymeric backbone, and a transition metalcatalyst; and (c) styrene/butadiene/styrene copolymer, and a transitionmetal catalyst, and vi) a seal layer coating or laminating the innermostsurface of the inner product contact sandwich layer; wherein thecontainer is a gable top carton or a rectangular carton.
 2. A rigidpaperboard container according to claim 1 wherein the polymeric backboneof the combination of a polymeric backbone, cyclic olefinic pendentgroups and linking groups linking the olefinic pendent groups to thepolymeric backbone is ethylenic and the linking groups are selected fromthe group consisting of: —O—(CHR)_(n)—; —(C═O)—O—(CHR)_(n)—;—NH—(CHR)_(n)—; —O—(C═O)—(CHR)_(n)—; —(C═O)—NH—(—CHR)_(n)—; and—(C═O)—O—CHOH—CH₂—O—; wherein R is hydrogen or an alkyl group selectedfrom the group consisting of methyl, ethyl, propyl and butyl groups andwhere n is an integer in the range from 1 to
 12. 3. A rigid paperboardcontainer according to claim 1 wherein the cyclic olefinic pendentgroups of the combination of a polymeric backbone, cyclic olefinicpendent groups and linking groups linking the olefinic pendent groups tothe polymeric backbone have the structure (I):

where q₁, q₂, q₃, q₄, and r are selected from the group consisting of—H, —CH₃, and —C₂H₅; and where m is —(CH₂)_(n)— with n being an integerin the range from 0 to 4; and wherein, when r is —H, at least one of q₁,q₂, q₃ and q₄ is —H.
 4. A rigid paperboard container according to claim1 wherein the polymeric backbone of the combination of a polymericbackbone, cyclic olefinic pendent groups and linking groups linking theolefinic pendent groups to the polymeric backbone comprises monomersselected from the group consisting of ethylene and styrene.
 5. A rigidpaperboard container according to claim 1 wherein the seal layer isselected from the group consisting of low density polyethylene polymer,linear low density polyethylene polymer, a blend of low densitypolyethylene polymer and linear low density polyethylene polymer, and acoextrusion of low density polyethylene polymer and linear low densitypolyethylene polymer.
 6. The paperboard container according to claim 1,wherein the container contains juice.
 7. The paperboard containeraccording to claim 6 wherein the container contains orange juice.